He is now arguing he should get a new trial because police searched his home without a warrant when they came to check on the well-being of his family.

In his appeal, filed at the state's Supreme Judicial Court, his lawyer Stephen Paul Maidman argued that evidence taken from the home was seized illegally.

Mr Maidman argues that two searches were carried out without warrants and the evidence seized as a result should have been suppressed during Entwistle's trial.

"The two warrantless entries into the defendant's house by the police violated the federal and state constitutions," he wrote in the appeal brief.

But prosecutors have said police were justified in entering the home because they were responding to the pleas of concerned relatives and friends.

They say Entwistle had become despondent after accumulating tens of thousands of dollars in debt and had complained about his sex life with his wife.

Entwistle's lawyer also argues that judge Diane Kottmyer did not thoroughly question potential jurors to determine whether they were biased against him after the case received intense local and international news coverage.

"That there was extraordinary prejudicial pre-trial publicity in this case that was both saturating and inflammatory, by Massachusetts and even national standards, cannot be legitimately disputed," Mr Maidman wrote in the appeal.

But Middlesex district attorney Gerry Leone, whose office prosecuted Entwistle, said he received a "true and just" trial.

"The crimes committed by Neil Entwistle against his wife Rachel and daughter Lillian Rose are to be condemned as horrific and unspeakable acts," Mr Leone said in a statement.

"He received a commendable defence and a fair and just trial under our laws."

Entwistle, a former IT consultant from Kilton, Worksop, left the US the day after the killings and later told police he had departed because he wanted to be consoled by his parents in the UK.

He said he found his wife and daughter cuddled together in bed, dead of apparent gunshot wounds, after he returned home from running errands.

Friends giving evidence said the couple appeared to have had a happy marriage and were both thrilled with their daughter.

Entwistle was jailed for what Ms Kottmyer described as "incomprehensible" crimes.

She also imposed a 10-year probation sentence for two firearms offences and ordered that Entwistle should not profit from his crimes by writing a book.